Electrochemical Impedance Spectroscopy for Online Satellite Battery Monitoring Using Square Wave Excitation

Electrochemical Impedance Spectroscopy was conducted on Li-Ion cells using a simple square current waveform as excitation signal, instead of the traditional sinusoidal sweep. Using a sampling rate of 1 kHz and a square wave period of 40 seconds, exploitable EIS data ranging from 0.025 Hz to 25 Hz could be extracted, which corresponds to the region where most of the useful data lies. Sensitivity of the method to sampling rate, square wave period and test current was explained, together with the effect of measurement noise on the final results. It was shown how current satellite technology could be used to produce such datasets in order to better estimate Battery State of Charge (SOC), State of Health (SOH) and Remaining Useful Lifetime (RUL).